A literature (“2002 New Technology of Matsushita Electric”, May 2003, pp. 155-159, (DDS-Equipped Backup Library), issued by R&D Planning Office) describes a data library device illustrated in FIG. 10. This data library device is configured as follows. A plurality of tape cassettes 1 are annularly arranged on a turn table 2. A turn table drive mechanism 3 allows the turn table 2 to rotate. An elevator mechanism 5 inserts/removes a target one of the tape cassettes 1 contained in garages 4 of the turn table 2 into/from a tape drive 6. Thus, data is read out from or written to the target tape cassette.